1. Field of Invention
The present invention relates a bottle-type plastic container that can be filled with liquid contents at a high temperature.
2. Description of Related Art
When a bottle-type container of a blow-molded plastic material, such as PET, is filled with liquid content at a high temperature of 80-95xc2x0 C., for example, it is generally inevitable that the shape of the container at its body changes significantly due to a pressure drop within the container. This occurs as a result of cooling of the contents to a room temperature. In the case of a bottle-type plastic container having a circular cross-section, for example, the peripheral wall of the body tends to be locally deflected inwards so that the original circular cross-section is deformed into a substantially triangular cross-section with rounded apexes. The appearance and/or commercial value of the product may be more or less impaired by the deformed cross-section of the body, even when the quality of the contents remains unchanged.
JP-A-07-172,423 discloses a bottle-type plastic container in which a pressure drop within the container is absorbed by an inward deflection of body walls that are provided with annular grooves having an arcuate cross-section. In this instance, the body is at least locally defined by relatively wide major surface walls formed with such annular grooves and relatively narrow, and substantially inflexible, corner walls. These walls are arranged alternately to each other to form a substantially quasi-octagonal cross-section. Those regions of the flexible major surface walls, which are circumscribed by the annular grooves, function as pressure change absorbing wall portions of the container.
The arrangement proposed in JP-A-07-172,423 proved to effectively absorb the pressure drop within the container having the above-mentioned particular cross-sectional shape. However, this measure may not always be applicable to eliminate the problem of the inward deflection of the body wall in a well-balanced manner, depending upon the cross-sectional shape of the body that may be designated by bottlers for enhancing an attractive appearance of the product, such as a substantially regular polygonal cross-sectional shape.
It would be desirable that a hot fill bottle-type plastic container filled with liquid content at a high temperature allows a well-balanced absorption of the pressure change within a container even when the body has a substantially regular cross-sectional shape.
To this end, according to the present invention, a bottle-type plastic container comprises a body and an opening at one end of the container that allows liquid contents to be charged into the container and emptied therefrom, wherein the body includes at least one body portion having a substantially regular polygonal cross-section defined by a plurality of generally flat walls. These walls of the body portion include flexible walls and less-flexible walls, which are arranged alternately in a circumferential direction of the body portion.
With the above-mentioned arrangement of the bottle-type plastic container according to the present invention, when the liquid contents initially filled at a high temperature are cooled to room temperature, a resultant pressure drop within the container is absorbed initially by a primary inward deflection of the flexible walls and subsequently by a secondary inward deflection of the less-flexible walls. Since the flexible walls and less-flexible walls of the body portion are arranged alternately to each other in a circumferential direction of the body portion, it is possible to effectively absorb the pressure drop within the container in a well-balanced manner, even when the body has a substantially regular cross-sectional shape.
The body may include a pair of body portions that are arranged in a longitudinal direction of the body one above the other. In this instance, it is preferred that the flexible walls and less-flexible walls of one body portion are arranged in alignment with the less-flexible walls and flexible walls of the other body portion, respectively.
It is preferred that the cross-section of the body portion is defined by a plurality of sides, the number of which is an even number of not less than four. Thus, for example, the body portion may have a substantially regular hexagonal cross-section.
The container according to the present invention may be formed by a conventional molding process, such as a biaxial orientation blow molding process or a direct blow molding process. The plastic material of the container may be one member selected from the group consisting of polyethylene terephthalate (PET) resin, polyamid resin, polycarbonate resin, polyacetal resin and polybuthylene terephthalate resin.
In the container according to the present invention, at least one body portion may be covered by a heat shrink label. Alternatively, or additionally, the plastic material of the container may form a laminated structure including a barrier layer.